COPPER(II)-POLY(L-HISTIDINE) AS AN ENZYME MODEL FOR L-ASCORBATE OXIDASE

The autoxidation catalyzed by copper(II)-poly(L-histidine) was studied by a rapid-mixing spectrophotometric method. The reaction obeys Michaelis-Menten kinetics. The double reciprocal plots of the velocity against the concentrations, i. e. the Lineweaver-Burk plots, of ascorbate and of oxygen gave a straight line. A kinetic analysis of the Lineweaver-Burk plot of the reaction reveals that the autoxidation of ascorbate by Cu(II)-PLH proceeds a so-called Ping-Pong mechanism. Copper(II) ion associates with PLH. The rate of ascorbate autoxidation appeared to depend on the concentration of copper(II) ion in the PLH phase, which is designated as the average binding number.